This application relates to a method for detection of analyte concentration using an electrochemical test strip, and to a meter and meter test strip combination for use in such a method.
Small disposable electrochemical test strips are frequently used in the monitoring of blood glucose by diabetics. Such test strips can also be employed in the detection of other physiological chemicals of interest and substances of abuse. In general, the test strip comprises at least two electrodes and appropriate reagents for the test to be performed, and is manufactured as a single use, disposable element. The test strip is combined with a sample such as blood, saliva or urine before or after insertion in a reusable meter, which contains the mechanisms for detecting and processing an electrochemical signal from the test strip into an indication of the presence/absence or quantity of the analyte determined by the test strip.
Electrochemical detection of glucose is conventionally achieved by applying a potential to an electrochemical cell containing a sample to be evaluated for the presence/amount of glucose, an enzyme that oxidizes glucose, such as glucose oxidase, and a redox mediator. As shown in FIG. 1, the enzyme oxidizes glucose to form gluconolactone and a reduced form of the enzyme. Oxidized mediator reacts with the reduced enzyme to regenerate the active oxidase and produce a reduced mediator. Reduced mediator is oxidized at one of the electrodes, and then diffuses back to either be reduced at the other electrode or by the reduced enzyme to complete the cycle, and to result in a measurable current. The measured current is related to the amount of glucose in the sample, and various techniques are known for determining glucose concentrations in such a system. (See, U.S. Pat. Nos. 6,284,125; 5,942,102; 5,352,2,351; and 5,243,516, which are incorporated herein by reference.)
Improvements in test strip design are driven by several considerations, including the need for accuracy and a desire for production of rapid results. The time required for correct measurement to occur, however, can be variable as a result of sample characteristics and variabilty of the test device. Thus, devices which perform a measurement at a fixed time after sample insertion have to make compromises in order to maximize the likelihood of sufficient time having passed. This compromise lengthens the time required to do a measurement, and may still fail to deal with samples and test devices that fail to conform to anticipated averages. Since performance of duplicate tests requires a level of user participation that may not be obtained, it would be desirable to have a glucose test system that did not make these compromises.